Apparatus and method for producing working fluid for a power plant

ABSTRACT

Apparatus and a method for forming a gas hydrate for use in the production of pressurised gas due to the decomposition of the gas-hydrate in a storage chamber, and for controlled delivery of the pressurised gas as working medium to a turbine engine which is preferably coupled to a generator for the production of electricity.

The present invention relates an apparatus and method for producingworking medium for supply to an engine of a power installation. Moreespecially the invention relates to the area of power-plant engineeringof electricity-generating installations for the transformation oflow-potential and high-potential thermal energy into mechanical andelectrical energy, and also in the area of a means of preparation of aworking medium for such installations.

TECHNICAL BACKGROUND

There exists an electricity-generating installation containing ahigh-potential heat source. The installation has a closed circuit withan intermediate heat-transfer medium, a power turbine, heat-exchangersfor heating and cooling the working medium. Patent USSR No. 70147, Int.class. F03G7/00, publ. 1948 applies.

There also exists an electricity-generating installation containing aturbine for driving a load, a cooler, a circulating pump and two or morechambers for preparing the working medium, all of the above connected bymeans of pipelines. The chambers are connected to the turbine and have aheater, a separator and sealing devices at the outlet. The circulationpump is connected to the cooler and to each of the chambers to form acircuit for the circulation of liquid. Patent USSR No. 1170180, Int.class FO125/00, publ. 1985 applies.

There exists a means for the preparation of the working medium of anelectricity-generating installation, consisting in the filling of anintermediate heat transfer medium circuit with a volatile liquid and itssubsequent evaporation in an heat-exchanger by air compressed in ancompressor and the supply of the vapour to the turbine. Patent USSR No.70147, Int. class F03G7/00, publ. 1948 applies.

There also exists a means for the preparation of the working medium ofan electricity-generating installation, including the filling of one ormore chambers with a liquid, the introduction into one of the chambersof an additional component and the raising of its pressure, the heatingof the working medium formed in it and, following the supply of theworking medium to the turbine, the performance of these operations inanother chamber. Patent USSR No. 1170180, Int. class F01K25/00, publ.1985 applies.

Further, U.S. Pat. No. 3943719 discloses apparatus for supplying workingmedium to an engine (e.g. turbine), this apparatus comprising generatingmeans for producing working medium and delivery means for supplying saidworking medium to an engine. In particular the generating meanscomprises reactor means for the formation of a compoung (i.e. hydride)from which the working medium (i.e. Hydrogen) is obtained, while storagemeans are provided for holding said compound formed by said reactormeans, said delivery means including control means for controlleddelivery of working medium from the storage means to the engine.

According to one aspect of the present invention there is providedapparatus for supplying working medium for a gas expansion enginecomprising generating means for producing working medium, storage meansfor the working medium, and delivery means for supplying the workingmedium to an engine from the storage means, the delivery means includingcontrol means for controlled delivery of the working medium from thestorage means to the engine wherein the generating means comprisesreactor means arranged and adapted for the formation of a gas-hydratefrom which the working medium for the engine is obtained, the storagemeans holding the gas hydrate formed by the reactor means, and a liquidrecirculation circuit is provided for recycling liquid discharged fromthe reactor means back to the reactor means, the recirculation circuitincluding a recirculating pump and a heat-exchanger. The method inparticular using water condensate from a steam turbo-generator plant forthe production of the gas hydrate (with a further component) in areaction chamber, the gas hydrate so produced being stored in suitablestorage means in readiness for the formation of the working medium.

DISCLOSURE OF THE INVENTION

The principal object of the present invention is to raise the efficiencyof an electricity-generating installation by means of the exclusion ofwasteful losses of heat and mechanical energy, the use in the workingcycle of low-potential and high-potential heat and the creation of anecologically sound system for the transformation of heat to work.

To meet this object there is provided apparatus for supplying workingmedium to a gas expansion engine, as set out in the appended claim 1.

Preferably, the storage means comprises a plurality of separatecontainers, the delivery means including conduit means for supplyingworking medium to the engine from the containers and in that the controlmeans comprise valves operable for sequential delivery of working mediumfrom the containers to the engine via said conduit meams.

In addition, the apparatus may be provided with a gas supercharger,connected to the containers so as to form one or more circuits for gasrecirculation. The containers may be constructed with one or moreexternal separators and/or one external reactors connected via agas-hydrate emulsion outlet to the containers, while the separator issituated at the outlet of the chambers and connected via its liquidoutlet to the inside volume of the chambers, which are in additionconnected to a circuit for the circulation of liquid. The apparatus caninclude a heater and cooler constructed in the form of a singleheat-exchange device, supplied intermittently from external sources withtwo heat-transfer media at different temperatures. The apparatus mayalso be fitted with an electrolyzer, and the load may take the form of agenerator, with the electrolyzer being connected to the generator andthe working-chamber being connected to an additional heat-exchanger soas to form an additional heat recovery path to add the heat produced byelectrolysis to the working media of the system before it enters theengine (turbine). The installation may be fitted with an additionalturbine, and the electrolyzer may be constructed to accept oxygen andhydrogen and be fitted with an oxygen outlet which is connected to theadditional turbine.

According to another aspect of the present invention there is provided amethod of producing a working medium for supply to a gas expansionengine comprising introducing liquid and an additional component such aswater and a gas into a reaction chamber to form by reaction agas-hydrate from which the working medium is obtained and storing thegas-hydrate so produced in storage means, wherein for maintainingdesirable conditions of reaction in the reaction chamber the liquiddischarged from the reaction chamber is passed in a recirculatingcircuit including heat exchanger means back to the reaction chamber.Thus the present invention can encompass the introduction into one ormore chambers filled with liquid of a low-pressure gaseous component,which is absorbed by the liquid to form a solid-phase compound, whichsubsequently when heated decomposes in the same chamber or anotherchamber and produces a high-pressure gas-phase working medium forelectricity-generating installation, which medium drives the turbine.The substances used for the liquid and gas-phase components are,respectively, water and a gas such as a methane-propane mixture, whichreacts with water to form a gas-hydrate, while (optimal) conditions ofheat-mass transferring process in the chamber are achieved by thewater's being recirculated and cooled by an external heat-transfermedium, and also by the recirculation of the gas which has not reacted.In addition, before the working medium is supplied to the turbine, itmay be additionally heated by a heat-transfer medium at a hightemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings wherein:

FIG. 1 shows schematically an electricity-generating installation inaccordance with a first embodiment of the present invention;

FIG. 2 shows schematically an electricity-generating installationaccording to a second embodiment;

FIG. 3 shows electrolyser apparatus which can be used in theinstallation of FIGS. 1 and 2;

FIG. 4 is a graph of the state of thermodynamic equilibrium of agas-hydrate compound, in particular the methane-propane mixture (CH₄ +C₃H₈)×6H₂ 0 with a relative specific weight of 0.6; and

FIGS. 5A, 5B and FIG. 6 show modifications.

Referring to FIG. 1, an electricity-generating installation comprises aturbine 3 for driving a load in the form of an electrical generator 4and two or more chambers 5, 6 constructed with a reactor for theformation of gas-hydrate from which the gaseous working medium for theturbine 3 is obtained, pipelines 1 and 2 serving for the supply ofworking medium to the turbine 3 and medium discharge therefromrespectively, the pipelines 1, 2 forming a closed circuit with theturbine 3 and chambers, 5, 6. The chambers 5, 6 include emulsators 7, 8and separators 5S, 6S in the upper section of the chambers 5, 6. Thechambers, 5, 6 are included via the circulation pumps 9, 10 in thecircuits for the circulation of liquid 11, 12, the circuit includingheat-exchange devices 13, 14, which are external selective heaters andcoolers supplied through the pipelines 15, 16 and the adjustablethree-phase valves 17, 18 from external sources intermittently with twoheat-transfer media at different temperatures. The substance used forthe heating heat-transfer medium may be a low potential heat-transferliquid such as water heated by means of waste heat from industrialinstallations, or by means of solar converters, thermosorbent heat-pumpinstallations, or the heat from the condensation of steam, for instance,in industrial and natural sources. The substance used for the coolingheat-transfer medium may be any fluid with a temperature lower than thesubstance H of the heating heat-transfer medium. The heat-transfer mediamay be water obtained from any suitable source, for example from variousdepths in reservoirs so as to obtain water at a suitable temperaturelevel. The temperature of the heating heat-transfer medium may be, forinstance, 28° C. (see FIG. 4, point B') and the temperature of thecooling heat-transfer medium, for instance, 4° C. (see FIG. 4, pointA'). The installation may be fitted with an additional heat-exchanger 19using a high temperature heat-exchange medium and installed prior to theturbine 3 for heating the working medium passing to the turbine 3. Thesubstance used as a high temperature heat-exchange medium may be theexhaust gases from internal combustion engines, the flue gases fromindustrial installations and so forth. The installation is fitted with agas-supercharger 20 or compressor connected to the chambers 5, 6 via theadjustable three-phase valve 21, and via the settable valves 22, 23 forrecirculating gas which has not reacted in the chambers 5, 6. Thegas-supercharger 20 is included in the recirculation circuits 24, 25with the common outlet pipe 26. The chambers 5, 6 are included in thegas circulation circuits 29, 30 which include settable closure valves 2728. The substance used as a working medium in the installation is agas-hydrate compound formed and decomposed in the installation, forinstance an 85 per cent methane plus 15 per cent propane mixture of thetype (CH₄ +C₃ H₈) * 6H₂ 0 with a relative specific weight of 0.6. It ispossible to use special additives, for example, glycol in the water,which increase the efficiency of the process by which the working medium(gas hydrate) is produced. For preparation of the working medium one ofthe chambers is filled with water, for instance chamber 5 (FIG. 1) viathe open valve 22 with valves 23 and 27 closed, and valve 21 closed toclose the circuit 24. Gas is passed through this water, for instance amethane-propane mixture, via the emulsator 7 until the pressure inchamber 5 is raised to the level required for the formation ofgas-hydrate, for instance 15 atmospheres (see point A in FIG. 4). Theformation of the gas-hydrate releases heat within the reactor chamber.In order to stabilise the reaction to form gas hydrate in chamber 5, thepump 9 pumps the water from chamber 5 through the heat-exchange device13, which is supplied with a cooling heat-transfer medium. At the sametime the supercharger 20 is used to recirculate the gas which has notreacted. The process of formation of the gas-hydrate is halted when thechamber is substantially filled with gas-hydrate. Following this, valve17 is used to introduce a hot (warm) heat-transfer medium into theheat-exchange device 13, and the heat is transferred to chamber 5, whichresults in the disassociation of the gas-hydrate under high-pressure.The pressurised gas which is released is separated from droplets ofwater by the separator 5S in the upper section of chamber 5. Thisresults in the establishment in chamber 5 of a working pressurecorresponding to the temperature of decomposition of the gas hydrate(see FIG. 4, point B), for instance 300 atmospheres. Following this thevalve 27 is opened and the high pressure gas is supplied to the turbine3 for the production of work and the driving of the generators, forinstance, of the generator 4. At the same time as gas is supplied toturbine 3 the heating of water in chamber 5 is continued. During thesupply of gas from chamber 5 to the turbine the operations describedabove for the production of gas-hydrate are performed in chamber 6,using the valves 23, 28 and the heat-exchange device 14. When thepressure begins to fall in chamber 5 due to all of the gas hydratehaving now decomposed, the valve 27 is closed, and the heating of waterin chamber 6 begins. After a working pressure has been developed inchamber 6, valve 28 is opened and the pressurised gas is supplied fromchamber 6 to the turbine 3. Where there is a source of ahigh-temperature heat-transfer medium the heat exchanger 19 is used tofurther raise the temperature of the gas prior to the turbine, therebyincreasing the power of the turbine. A regular supply of gas to theturbine 3 and a minimal fluctuation of pressure in the circuits areachieved by the installation of the requisite number of the abovementioned reactor chambers and their operation in phased sequence. Theinstallation may be constructed with an external reactor 54 (FIG. 2),connected via its outlet 32 through the circulation pump 33 and throughthe adjustable valves 34 and 35 to the chambers 5A and 6A. In turn thechambers 5A, 6A are connected via the adjustable valves 36, 37 and thepipeline 55 to the cooler 38, and thereby with the circuit 39 for thecirculation of liquid and with the pump 39A, which is connected to thelower section 56 of the reactor 54. The supercharger 20 is connected tothe upper section 31 of the reactor 54, to the exhaust pipe 2 and to theemulsator 7A so as to form the gas circulation circuit 40. Theinstallation may include an external separator 41, connected to theupper sections of the chambers 5, 6 and connected via its exit pipe 42to the liquid circulation circuit 43 which includes the heater 44, usinga low-potential external heat-transfer medium, the pump 45, and theadjustable valves 46-49, connected to the chambers 5, 6. In additionwhen a large number of chambers is used the separator 41 performs thefunctions of a receiver, which supplies a regular supply of gas to theturbine 3.

The installation may be fitted with an electrolyser 50, while the loadof turbine 3 takes the form of the generator 4. In this case the workingchamber of the electrolyser 50 is connected to the additionalheat-exchanger 19, using a high-temperature heat-transfer medium, so asto form the additional circulation circuit 51 for the return of the heatof electrolysis to the work cycle of the installation. The electrolyser50 may be equipped, for instance for the production of hydrogen andoxygen, with an outlet 52 for oxygen connected to an additional turbine53. For the installation constructed with an external reactor 54 and aseparator 41, the formation of the gas-hydrate is carried out outsidethe storage chambers 5, 6. This is done by filling the reactor 54 andthe liquid circulation circuit 39 with water distilled (which maycontain additives) from an external storage tank. When the system hasbeen filled with water the above-mentioned working gas is pumped throughthe emulsator 7A with the valves 34, 35 closed. At the same time wateris continuously circulated through the cooler 38 and the gas which hasnot reacted is circulated using the impeller fan 20. The gas-hydrateemulsion formed in the reactor 54 is pumped by the pump 33 into one ofthe chambers, for instance chamber 5A, with the valve 34 open and thevalve 27 closed. As the gas-hydrate fills the chamber is displaces theremaining water along the pipe-line 55 into the circuit 39. Followingthis, the valves 46, 48 are opened and the valves 34, 36 are closed, andthe water is pumped by the pump 45 through the heater 44. At the sametime in the chamber 5A the gas-hydrate is dissociated under highpressure, and the gas accumulates in the storage section of chamber 5.When the temperature of the water being pumped through the heater 44 isstabilised, the valve 27 is opened and the gas at working pressureenters the separator 41, where it is separated from water droplets andthen it is introduced via the pipe 1 into the turbine 3. At the sametime the pumping of water through the heater 44 continues. When all thegas has emerged under a constant pressure from the chamber 5A, thevalves 46 and 48 are closed. Following this, the process described aboveis repeated using chamber 6A, and chamber 6A is filled with gas-hydrate.The spent gas from the turbine is led along the pipeline 2 into theemulsator 7A and the gas bubbles through a layer of water in the rector54, with the result that the gas-hydrate is produced continuously in theprocess of the installation's operation.

If an external separator 41 is installed when there is a large number ofchambers, it may also be used as a receiver which excludes fluctuationsin the pressure of the gas in the system. If the installation uses anelectrolyser 50, its working chamber is connected to an additionalheat-exchanger 19, using a high-temperature heat-transfer medium, whichmakes it possible to exploit the heat of electrolysis. In accordancewith the invention, the installation possesses a high degree ofoperational reliability as a result of the absence of high thermal ormechanical stresses, it allows the use of inexpensive constructionmaterials, and its working cycle is automatically regulated to a highdegree. The invention should enable a considerable reduction in the costof producing electricity.

FIG. 5A shows a modification to provide more efficient formation ofgas-hydrate, and also give a greater power generating facility. Themodification operates on an induction principle by drawing or suckingthe gas into the water flow, and the arrangement is described as aliquid-jet (or stream) inducer or injector. Thus, there is provided amixing chamber 60 in a throat with an inlet manifold 61 of larger crosssection to one side while a diverging discharge 62B at the other sideleads to the chambers 5, 6 or 54. An inlet pipe 63 for the high pressurerecirculated water extends into the manifold 61 and has a dischargenozzle 63A located at the converging inlet 62A of the throat, while afurther inlet pipe 64 feeds the gas to the manifold 61. In operation,the recirculated high-pressure cooled water W is discharged from thenozzle 63A, and the gas in the manifold 61 is sucked into the flowingwater via jet inlet 62A and mixing of the gas and water occurs in themixing chamber 60 resulting in efficient and effective formation of gashydrate.

FIG. 5A shows a single liquid jet inducer, but it would be possible toemploy a bank (or battery) of such devices for greater output of gashydrate and consequently greater power capacity, and FIG. 5B shows theprovision of such a battery. In this case the inducer bank is located atzone 54A in the chamber 54 and comprises an aligned array of throatsdefining a plurality of mixing chambers 60. The high-pressure cooledwater is fed to a manifold formation 63M in the chamber 54 having aplurality of nozzle discharges 63A each corresponding to a relevantmixing chamber 60 (all generally as in FIG. 5A). while the gas is led toan inlet 64A appropriately located on the chamber 54. Operation of theinducer bank of FIG. 5B is exactly similar to the inducer of FIG. 5A.

FIG. 6 shows an alternative power generating arrangement usable in theinventive system, wherein two or more expansion engines in the form ofturbines 3,3'. . . are arranged in series with working medium producedfrom gas hydrate passing serially through the turbines, and anadditional heat exchanger 19' is located in the flow path betweensuccessive turbines 3,3' for intermediate heating of the working mediumpassing between the turbines to provide greater efficiency in theoperation of the power generating arrangement.

INDUSTRIAL APPLICATIONS

The invention is intended for the creation of permanent, ecologicallysound electricity-generating installations, utilising renewable naturalsources of low-potential thermal energy. The invention may be used incombination with various power-intensive technological processes whichproduce waste heat, which is transformed in the installation into usefulwork, with a high degree of efficiency, for instance for theeconomically effective production of hydrogen.

The invention could of course be used in installations other thanelectricity-generating installations, for example, in a pumpinginstallation, and the invention can be utilised to provide workingmedium for a variety of gas expansion engines generally.

We claim:
 1. Apparatus for supplying working medium for a gas expansionengine comprising:generating means for producing working medium, storagemeans for the working medium, and delivery means for supplying saidworking medium to the gas expansion engine from the storage means, saiddelivery means including control means for controlled delivery of theworking medium from the storage means to the engine wherein saidgenerating means comprises reactor means arranged and adapted for theformation of a gas-hydrate from which the working medium for the engineis obtained, said storage means holding the gas hydrate formed by saidreactor means, and a liquid recirculation circuit is provided forrecycling liquid discharged from the reactor means back to the reactormeans, said recirculation circuit including a recirculating pump and aheat-exchanger.
 2. Apparatus as claimed in claim 1, wherein the storagemeans comprises a plurality of separate containers, the delivery meansincluding conduit means for supplying working medium to the engine fromthe containers, and wherein the control means comprise valves operablefor sequential delivery of working medium from the containers to theengine via said conduit means.
 3. Apparatus as claimed in claim 2,wherein each storage container has a gas outlet connected to the inletof the engine, the outlet of the engine being connected to the gas inletof the reactor means.
 4. Apparatus as claimed in claim 2, wherein thecontainers are constructed with at least one external separator,connected via a gas-hydrate emulsion outlet to the containers, the atleast one separator being situated at the outlets of the containers andhaving a liquid outlet connected to the liquid inlets of the containers,which are in addition connected to the circuit for the circulation ofliquid.
 5. Apparatus as claimed in claim 2, further comprising returnconduit means for return of expanded working medium from the engine tothe reactor means, whereby the engine and the working medium supplyapparatus operate in a closed cycle.
 6. Apparatus as claimed in claim 2,wherein the containers are constructed with at least one externalseparator and at least one external reactor, connected via a gas-hydrateemulsion outlet to the containers, the at least one separator beingsituated at the outlets of the containers and having a liquid outletconnected to the liquid inlets of the containers, which are in additionconnected to the circuit for the circulation of liquid.
 7. Apparatus asclaimed in claim 1, further comprising return conduit means for returnof expanded working medium from the engine back to the reactor meanswhereby the engine and the working medium supply apparatus operate in aclosed cycle.
 8. Apparatus as claimed in claim 1, wherein the heatexchanger comprises a cooler.
 9. Apparatus as claimed in claim 8,wherein the heat exchanger comprises a heater and a cooler, the heaterand the cooler being constructed in the form of an integralheat-exchange device, supplied intermittently from the external sourceswith at least two heat-transfer media at different temperatures. 10.Apparatus as claimed in claim 1, wherein the heat exchanger comprises aheater.
 11. Apparatus as claimed in claim 10, wherein the heat exchangercomprises a heater and a cooler, the heater and the cooler beingconstructed in the form of an integral heat-exchange device, suppliedintermittently from external sources with at least two heat-transfermedia at different temperatures.
 12. Apparatus as claimed in claim 1,wherein the reactor means includes a separator.
 13. Apparatus as claimedin claim 1, wherein the reactor means include an emulsator. 14.Apparatus as claimed in claim 1, further comprising at least one circuitfor the recirculation of unreacted gas to the reactor means and a gasimpeller located in the at least one circuit.
 15. Apparatus as claimedin claim 1, further including an additional heat-exchanger, using ahigh-temperature heat-transfer medium, installed immediately prior tothe engine, to heat the working medium passing to the engine. 16.Apparatus as claimed in claim 15, further comprising an electrolyzersupplying heating medium to said additional heat exchanger therebyforming an additional circulation circuit, and an electric power sourcefor the electrolyzer.
 17. Apparatus as claimed in claim 16 wherein saidelectric power source comprises a generator driven by the gas expansionengine, the gas expansion engine being supplied with working medium fromsaid storage means.
 18. Apparatus as claimed in claim 17, furtherincluding an additional turbine, the electrolyzer being equipped with anoxygen outlet connected to the additional turbine.
 19. Apparatus asclaimed in claim 17, further comprising an additional turbine while theelectrolyzer is equipped with a hydrogen outlet connected to theadditional turbine.
 20. Apparatus as claimed in claim 17, furthercomprising an additional turbine while the electrolyzer is equipped withan oxygen and hydrogen outlet connected to the additional turbine. 21.Apparatus as claimed in claim 1, wherein there is provided one or moreliquid-jet compressor devices for mixing water and gas for the formationof gas hydrate.
 22. Apparatus as claimed in claim 21, wherein a bank ofsaid compressor or inducer devices is present; said bank including analigned array of throat means defining a plurality of mixing chambersfor gas and water, a manifold receiving recirculated water and providedwith a plurality of discharge nozzles each corresponding to a relevantmixing chamber, and means for supplying gas so that a water jet orstream discharge from said nozzles draws the gas for mixing with thewater in said mixing chambers.
 23. Apparatus as claimed in claim 21,wherein a bank of said inducer devices is present; said bank includingan aligned array of throat means defining a plurality of mixing chambersfor gas and water, a manifold receiving recirculated water and providedwith a plurality of discharge nozzles each corresponding to a relevantmixing chamber, and means for supplying gas so that a water jet orstream discharge from said nozzles draws the gas for mixing with thewater in said mixing chambers.
 24. Apparatus as claimed in claim 1wherein there is provided one or more inducer devices for mixing waterand gas for the formation of gas hydrate.
 25. A power installationincluding a gas expansion engine and apparatus for supplying workingmedium for the gas expansion engine, said apparatus comprisinggenerating means for producing working medium, storage means for theworking medium, and delivery means for supplying said working medium tothe gas expansion engine from the storage means, said delivery meansincluding control means for controlled delivery of the working mediumfrom the storage means to the engine wherein said generating meanscomprises reactor means arranged and adapted for the formation of agas-hydrate from which the working medium for the engine is obtained,said storage means holding the gas hydrate formed by said reactor means,and a liquid recirculation circuit is provided for recycling liquiddischarged from the reactor means back to the reactor means, saidrecirculation circuit including a recirculating pump and aheat-exchanger.
 26. A method of producing a working medium for supply toa gas expansion engine, comprising:introducing liquid and an additionalcomponent and a gas into a reaction chamber to form by reaction agas-hydrate from which the working medium is obtained and storing thegas-hydrate so produced in storage means, and passing the liquiddischarged from the reaction chamber in a recirculating circuitincluding heat exchanger means to maintain desirable conditions ofreaction in the reaction chamber.
 27. A method as claimed in claim 26,wherein the liquid is cooled in said recirculating circuit.
 28. A methodas claimed in claim 26, wherein the liquid is heated in saidrecirculating circuit.
 29. A method as claimed in claim 26, wherein gasthat has not reacted is recirculated to the reaction chamber.
 30. Amethod as claimed in claim 26, wherein said additional componentcomprises a working gas capable of producing gas hydrate.
 31. A methodas claimed in claim 26, further comprising the step of heating theworking medium by high temperature heating means prior to delivery to anengine.
 32. A method as claimed in claim 26, wherein said additionalcomponent comprises methane propane.